This invention relates to a thermodynamic system for effectively and economically removing waste heat from space within a building or other enclosed structure containing a source of the waste heat. The system may comprise one or more communication transmitters, for transferring the heat to another location outside the structure where the heat is discarded, or dumped, into the ambient air.
In particular, this invention relates to a system for accomplishing removal of considerable waste heat from space containing large communication transmitters by conveying the heat to another location. If further heat removal or cooling is desired to supplement the basic thermodynamic action of the system, a conventional air conditioner of relatively small cooling capacity can be set into operation to provide total cooling otherwise available only from a much larger air conditioner. The system alone in many applications can handle all of the waste heat plus the normal building heat load.
The present Naval Facilities Engineering Division criteria for the environmental control of communication transmitter facilities requires ventilation to carry away the waste heat produced by the facility transmitters. Concurrently, the operator of the transmitter facility is provided an acceptable working environment by the expedient of separating the front, or operator side, of each transmitter from the rear and top sides of each transmitter by a solid partition that forms a corridor between two rows of transmitters that face each other. The corridor is air conditioned while hot air (waste heat) is exhausted from the top of each transmitter and ventilating air passes through intake apertures in the side of each transmitter. The space behind each transmitter row is used primarily as an air plenum. This entire arrangement has become known as the "plenum system". As compared to a system where the transmitters occupy space in any arrangement (not necessarily in facing rows) and where the waste heat is discharged into the space occupied by an operator which is fully air conditioned to remove heat from the space, the plenum system is much less costly in both first cost and operating cost. The plenum system, however, is not a panacea, and has certain drawbacks and limitations, to wit, (1) It requires a building configuration that contains a number of long, narrow wings so that outside air in large quantities can be admitted (i.e., forced-by-fans) into the plenum space behind each row of transmitters. A building of this configuration is not economical on a square foot basis; (2) With the front faces of the transmitters protruding into an air conditioned corridor and with the inside of each transmitter being flushed with the unconditioned outside air that often contains large quantities of moisture (high humidity); condensation of water from the air becomes a problem. This situation requires careful limitations on how cool the conditioned corridor can become and an environment tempering arrangement for the ventilating air where some of the waste heat in the exhaust air is used to warm the incoming air by throttling the quantity of outside air and mixing the remainder with some of the waste heat to prevent high humidities. This method of avoiding condensation of moisture from air is not well understood by the transmitter operators since it requires an understanding of the psychometric properties of air. As a result, the usual thinking is (a) the cooler the better, and (b) the more ventilation the better. The result of this thinking is that some transmitters have been found with an inch of water collected in the bottom. This, of course, is a situation that becomes much worse, with further water collected, when a transmitter is turned off for maintenance purposes and access panels are removed to provide openings into the corridor of opposed transmitters. (3) Access for maintenance is quite limited since one must move from the front of a transmitter to one end of the corridor, then through a door into the plenum and on to the rear of the transmitter to be serviced. (4) Much of the transmitter maintenance is accomplished through access panels on the rear of a row of transmitters. This means that work must be done in the unconditioned plenum that is elevated in temperature from heat supplied by the outside air and supplied by the operation of the other transmitters sharing the plenum and, if properly operated, from tempering that is supposed to maintain a plenum temperature of 90.degree. Fahrenheit regardless of outside air temperatures that may be below 90.degree. Fahrenheit. Although operators will debate the findings, it has been technically established that the transmitters which are procured to meet MIL-E-16400 and a temperature of 122.degree. Fahrenheit (50.degree. C.) will operate fine at 90.degree. Fahrenheit, a value that gives a large margin of safety for transmitter operation, and which temperature is 5.degree. Fahrenheit above the worst dew point found anywhere in the world per MIL-STD-210, "Climatic Extremes for Military Equipment." To this day no plenum system has ever worked for very long due to well intentioned but misguided tampering with control settings by operators. (5) The large quantities of air necessary to carry the waste heat out of the plenum must be filtered to a reasonable degree to remove dust, insects and other contaminants. This requires many filters that occupy much of the outside wall area of the building housing the transmitters. It has been found that throwaway filters, although cheap, are marginally adequate for the job and somehow never seem to be in stock when needed. Cleanable filters, usually metal, never get cleaned and oiled due to lack of manpower and some rust and corrode away from the combined effects of dirt and moist air. Many ventilating systems are either choked for air or are operating without filters.
The present invention provides a primary waste heat transfer system that will permit the use of any building configuration for a facility of communication transmitters, or comparable heat generating equipment; permit easier access to the transmitters, or comparable equipment, and will result in a closed-to-the-outside air, fully-air-conditioned-inside environment that will result in much less transmitter maintenance, better retention rate for experienced technician operators, a first and operating cost for the system comparable to ventilation and much less costly than 100 percent full air conditioning both in first and operating cost.
So-called thermosiphon heat exchanger systems are known and are briefly described on pages 34.14 through 34.17 of the 1979 Equipment Handbook of the American Society of Heating, Refrigerating, and Air-Conditioning Engineers, Inc. (ASHRAE). Two types of such systems exist, and are discussed on pages 34.14 through 34.17. The coil loop thermosiphon depicted in FIG. 31 on page 34.16 consists of a refrigerant working fluid which circulates in a closed-loop path between similar heat exchange units which may be designated respectively as an evaporator unit and as a condenser unit. This type of system achieves a thermosiphon action characterized by heat absorption as the working fluid evaporates in one unit and by heat release as the working fluid condenses in the other unit. The net result is heat transfer from one location to another.
So far as the applicant is aware, the above-described thermosiphon heat exchanger system is not in use today even though it has attractive simplicity. Possible reasons for the nonuse of such a system are many. One possible reason is that most, if not all, existing applications for such a system are inherently inefficient and the evolution of air conditioning technology has seen the use of various pumps, etc. to transfer heat from a space to be cooled (e.g., a warm room in summer) to another location (e.g., outside a home) where the heat is released. Such a system operates within certain well defined parameters of temperature and pressure and requires use of a refrigerant that does not consume much space so that compactness of the air-conditioning unit is attained. Such a system goes unused in winter time when the desired result is to transfer heat from the cold outside to the warmer inside of a room in a house, for example. Such a system could not perform the function of the present invention which is used to transfer very large quantities of waste heat from a localized source inside an enclosed structure when the outside air is either warmer or cooler than the inside air.
Heat pumps are known devices that may be said to transfer heat from outside to an indoor location and differ from the present system which transfers waste heat from an indoor location to an an outside location.
Automobile passenger compartment air conditioning systems remove heat from a passenger compartment. These systems utilize a compressor pump and could not utilize the present invention which does not utilize a pump nor a comparable refrigerant.
Systems shown in U.S. Pat. Nos. 3,507,320 and 4,340,030 do not perform the same function performed by the novel thermodynamic system of the present invention, although various components of the new system have been known for many, many years. U.S. Pat. No. 4,340,030, for example, discloses a solar heating system that employs a flooded evaporator, a condenser, a refrigerant reservoir, and a pump. A variation of this system dispenses with the pump when the system piping lies in one horizontal plane. U.S. Pat. No. 3,507,320, for example, discloses a heating and cooling system utilizing heat from a lighting system and does not disclose a thermodynamic waste heat transfer system.